Potential new targets in arthritis therapy: interleukin (IL)-17 and its relation to tumour necrosis factor and IL-1 in experimental arthritis

Proinflammatory cytokine expression profile in degenerated and herniated human intervertebral disc tissues

OBJECTIVE

Prior reports document macrophage and lymphocyte infiltration with proinflammatory cytokine expression in pathologic intervertebral disc (IVD) tissues. Nevertheless, the role of the Th17 lymphocyte lineage in mediating disc disease remains uninvestigated. We undertook this study to evaluate the immunophenotype of pathologic IVD specimens, including interleukin-17 (IL-17) expression, from surgically obtained IVD tissue and from nondegenerated autopsy control tissue.

METHODS

Surgical IVD tissues were procured from patients with degenerative disc disease (n = 25) or herniated IVDs (n = 12); nondegenerated autopsy control tissue was also obtained (n = 8) from the anulus fibrosus and nucleus pulposus regions. Immunohistochemistry was performed for cell surface antigens (CD68 for macrophages, CD4 for lymphocytes) and various cytokines, with differences in cellularity and target immunoreactivity scores analyzed between surgical tissue groups and between autopsy control tissue regions.

RESULTS

Immunoreactivity for IL-4, IL-6, IL-12, and interferon-gamma (IFNgamma) was modest in surgical IVD tissue, although expression was higher in herniated IVD samples and virtually nonexistent in control samples. The Th17 lymphocyte product IL-17 was present in >70% of surgical tissue fields, and among control samples was detected rarely in anulus fibrosus regions and modestly in nucleus pulposus regions. Macrophages were prevalent in surgical tissues, particularly herniated IVD samples, and lymphocytes were expectedly scarce. Control tissue revealed lesser infiltration by macrophages and a near absence of lymphocytes.

CONCLUSION

Greater IFNgamma positivity, macrophage presence, and cellularity in herniated IVDs suggests a pattern of Th1 lymphocyte activation in this pathology. Remarkable pathologic IVD tissue expression of IL-17 is a novel finding that contrasts markedly with low levels of IL-17 in autopsy control tissue. These findings suggest involvement of Th17 lymphocytes in the pathomechanism of disc degeneration.

Synovial effusion and synovial fluid biomarkers in psoriatic arthritis to assess intraarticular tumor necrosis factor-α blockade in the knee joint

INTRODUCTION

The purpose of this study was the evaluation of synovial effusion (SE), synovial fluid (SF) and synovial tissue (ST) biomarkers in relation to disease activity indexes to assess the response to intraarticular (IA) tumor necrosis factor (TNF)-α blockers in psoriatic arthritis (PsA).

METHODS

Systemic and local disease activity indexes (disease activity score (DAS); the Ritchie articular index (mRAI), erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP); Thompson articular (THOMP) and joint articular (KJAI)-Index ) and ST samples were assessed at baseline, throughout treatment, and during the follow-up in 14 patients affected with PsA who underwent IA injections (0.5 ml to 12.5 mg) in the knee joint of etanercept (E) or placebo (P) once every two weeks for a 10-week period. Total SF white blood cell (WBC) counts (WBC/μl) and SF cytokine/chemokine (CK/CCK) levels were measured before IA-E at baseline, after IA-E, and as long as there were adequate amounts of SF for knee aspiration (post). Characterization of synovial mononuclear cell infiltration and synovial vessels was carried out in 8 out of 14 knees by staining serial sections of synovial tissue biopsies for CD45, CD3, CD68, CD31 and CD105.

RESULTS

At baseline, CRP and/or ESR were significantly correlated with SF-CK (interleukin- (IL-)1β, IL-1Ra, IL-6, IL-8) and CCK (CCL3). Post-IA injections, there was a decrease in SE in the knees in which aspiration following IA-E injection was possible as well as a significant reduction in SF WBC/μl and in SF-CK (IL-1β, IL-1Ra, IL-6 and IL-22). Pre- and post-IA-E injections, there were significant correlations between ST markers and SF-CK (IL-1β with CD45; IL-1β and IL-6 with CD31) and between SF-CCK (CCL4 and CCL3 with CD3). At the end of the study, there was a significant reduction in disease activity indexes (CRP, DAS, RAI, THOMP, KJAI) as well as in the ST markers (CD45; CD3).

CONCLUSIONS

Synovial effusion regression is a reliable indicator of the response to IA TNF-α blockers in PsA patients as it is confirmed by the correlation between SF biomarkers to disease activity and synovial tissue inflammation.

Protein kinase C isoforms zeta and iota mediate collagenase expression and cartilage destruction via STAT3- and ERK-dependent c-fos induction

The protein kinase C (PKC) signaling pathway is a major regulator of cellular functions and is implicated in pathologies involving extracellular matrix remodeling. Inflammatory joint disease is characterized by excessive extracellular matrix catabolism, and here we assess the role of PKC in the induction of the collagenases, matrix metalloproteinase (MMP)-1 and MMP-13, in human chondrocytes by the potent cytokine stimulus interleukin-1 (IL-1) in combination with oncostatin M (OSM). IL-1 + OSM-stimulated collagenolysis and gelatinase activity were ameliorated by pharmacological PKC inhibition in bovine cartilage, as was collagenase gene induction in human chondrocytes. Small interfering RNA-mediated silencing of PKC gene expression showed that both novel (nPKC delta, nPKC eta) and atypical (aPKC zeta, aPKC iota) isoforms were involved in collagenase induction by IL-1. However, MMP1 and MMP13 induction by IL-1 + OSM was inhibited only by aPKC silencing, suggesting that only atypical isoforms play a significant role in complex inflammatory milieus. Silencing of either aPKC led to diminished IL-1 + OSM-dependent extracellular signal-regulated kinase (ERK) and signal transducer and activator of transcription (STAT) 3 phosphorylation, and c-fos expression. STAT3 gene silencing or ERK pathway inhibition also resulted in loss of IL-1 + OSM-stimulated c-fos and collagenase expression. Silencing of c-fos and c-jun expression was sufficient to abrogate IL-1 + OSM-stimulated collagenase gene induction, and overexpression of both c-fos and c-jun was sufficient to drive transcription from the MMP1 promoter in the absence of a stimulus. Our data identify atypical PKC isozymes as STAT and ERK activators that mediate c-fos and collagenase expression during IL-1 + OSM synergy in human chondrocytes. aPKCs may constitute potential therapeutic targets for inflammatory joint diseases involving increased collagenase expression.

Differing effects of exogenous and endogenous hydrogen sulphide in carrageenan-induced knee joint synovitis in the rat

BACKGROUND AND PURPOSE

Recent findings suggest that the noxious gas H(2)S is produced endogenously, and that physiological concentrations of H(2)S are able to modulate pain and inflammation in rodents. This study was undertaken to evaluate the ability of endogenous and exogenous H(2)S to modulate carrageenan-induced synovitis in the rat knee.

EXPERIMENTAL APPROACH

Synovitis was induced in Wistar rats by intra-articular injection of carrageenan into the knee joint. Sixty minutes prior to carrageenan injection, the rats were pretreated with indomethacin, an inhibitor of H(2)S formation (DL-propargylglycine) or an H(2)S donor [Lawesson's reagent (LR)].

KEY RESULTS

Injection of carrageenan evoked knee inflammation, pain as characterized by impaired gait, secondary tactile allodynia of the ipsilateral hindpaw, joint swelling, histological changes, inflammatory cell infiltration, increased synovial myeloperoxidase, protein nitrotyrosine residues, inducible NOS (iNOS) activity and NO production. Pretreatment with LR or indomethacin significantly attenuated the pain responses, and all the inflammatory and biochemical changes, except for the increased iNOS activity, NO production and 3-NT. Propargylglycine pretreatment potentiated synovial iNOS activity (and NO production), and enhanced macrophage infiltration, but had no effect on other inflammatory parameters.

CONCLUSIONS AND IMPLICATIONS

Whereas exogenous H(2)S delivered to the knee joint can produce a significant anti-inflammatory and anti-nociceptive effect, locally produced H(2)S exerts little immunomodulatory effect. These data further support the development and use of H(2)S donors as potential alternatives (or complementary therapies) to the available anti-inflammatory compounds used for treatment of joint inflammation or relief of its symptoms.

ANTI-CD3 therapy expands the numbers of CD4+ and CD8+ Treg cells and induces sustained amelioration of collagen-induced arthritis

OBJECTIVE

To assess the therapeutic potential of anti-CD3 monoclonal antibodies (mAb) for rheumatoid arthritis, using collagen-induced arthritis as an animal model.

METHODS

Arthritis was induced in DBA/1 mice by immunization with type II collagen. After disease onset, a single injection of anti-CD3 mAb (20 microg/mouse) was administered, and arthritis severity was monitored over a 10-day period.

RESULTS

Anti-CD3 mAb treatment resulted in a sustained reduction in disease activity, which was associated with an increase in the proportion of naturally occurring CD4+CD25+FoxP3+ regulatory T (Treg) cells and the generation of a population of CD8+CD25+FoxP3+ Treg cells. Anti-CD3 mAb treatment did not alter the capacity of CD4+ Treg cells to suppress effector T cell proliferation and interferon-gamma (IFNgamma) production in vitro. However, CD4+ Treg cells from both anti-CD3 mAb-treated and control mice were unable to suppress interleukin-17 (IL-17) production. In contrast, CD8+ Treg cells induced by anti-CD3 therapy suppressed IL-17 production as well as CD4+ T cell proliferation and IFNgamma production.

CONCLUSION

These results show that anti-CD3 mAb treatment has important therapeutic potential for rheumatoid arthritis and has the capacity to generate antiarthritic CD8+ Treg cells and expand the relative numbers of CD4+ Treg cells.

Overexpression of CXC chemokine ligand 14 exacerbates collagen-induced arthritis

CXCL14 is a relatively new chemokine with unidentified receptor and undefined function. Recently, we found that CXCL14 is upregulated in arthritic joints in a mouse model of autoimmune arthritis, collagen-induced arthritis. To examine the role of CXCL14 in the development and pathogenesis of autoimmune arthritis, we have generated transgenic (Tg) mice that overexpress CXCL14 under control of phosphoglycerate kinase promoter. The results showed that CXCL14-Tg mice developed more severe arthritis compared with wild-type controls. The draining lymph nodes of CXCL14-Tg mice were significantly enlarged and contained an increased number of activated T cells, particularly the CD44(+)CD62L(low) effector memory cells. In addition, T cells from CXCL14-Tg mice exhibited an enhanced proliferative response against collagen II and produced higher levels of IFN-gamma but not IL-4 or IL-17. CXCL14-Tg mice also had elevated levels of IgG2a autoantibodies. These findings indicated that CXCL14 plays an important role in the autoimmune arthritis, which may have an implication in understanding the pathogenic mechanisms of rheumatoid arthritis in humans and, ultimately, therapeutic interference.

Kitasato symposium 2009: new prospects for cytokine inhibition

The Kitasato Symposium 2009: New Prospects for Cytokine Inhibition was held in Berlin, Germany from 7 to 9 May 2009. The key aims of this meeting were to bring together a group of front-line researchers and rheumatologists to evaluate the use of cytokine blockade and to examine the role of certain cytokines in the pathogenesis of rheumatoid arthritis and other autoimmune diseases. A keynote lecture delivered by Professor Jean-Michel Dayer provided an up-to-date overview of the interactions occurring between the immune system and acute phase proteins. Other speakers discussed the role of cytokines in rheumatoid arthritis, including their role in joint destruction, as well as their regulatory role upon T cells and B cells. The involvement of cytokines in other autoimmune diseases was also addressed.

IRF4 and its regulators: evolving insights into the pathogenesis of inflammatory arthritis?

Accumulating evidence from murine and human studies supports a key role for interleukin-17 (IL-17) and IL-21 in the pathogenesis of inflammatory arthritis. The pathways and molecular mechanisms that underlie the production of IL-17 and IL-21 are being rapidly elucidated. This review focuses on interferon regulatory factor 4 (IRF4), a member of the IRF family of transcription factors, which has emerged as a crucial controller of both IL-17 and IL-21 production. We first outline the complex role of IRF4 in the function of CD4(+) T cells and then discuss recent studies from our laboratory that have revealed a surprising role for components of Rho GTPase-mediated pathways in controlling the activity of IRF4. A better understanding of these novel pathways will hopefully provide new insights into mechanisms responsible for the development of inflammatory arthritis and potentially guide the design of novel therapeutic approaches.

IL-17 as a future therapeutic target for rheumatoid arthritis

The discovery of interleukin (IL)-17 and its major cell source, the type 17 T-helper (TH17) lymphocyte, has been a major step in the understanding of erosive arthritis. This Review summarizes current knowledge of the role of IL-17 in this context derived from both animal models and studies in patients with rheumatoid arthritis. Evidence shows that IL-17 is present at sites of inflammatory arthritis and that, in synergistic interactions, it amplifies the inflammation induced by other cytokines, primarily tumor necrosis factor. In several animal models of arthritis, inhibition of IL-17 limits inflammation and joint erosion. Initial observations from phase I trials show that signs and symptoms of RA are significantly suppressed following treatment with anti-IL-17 antibodies, without notable adverse effects. The emergence of IL-17 blockade as a future therapy in rheumatoid arthritis is highlighted, along with the potential goals and limitations of this therapeutic approach.

RANKL inhibition by osteoprotegerin prevents bone loss without affecting local or systemic inflammation parameters in two rat arthritis models: comparison with anti-TNFalpha or anti-IL-1 therapies

INTRODUCTION

Rat adjuvant-induced arthritis (AIA) and collagen-induced arthritis (CIA) feature bone loss and systemic increases in TNFalpha, IL-1beta, and receptor activator of NF-kappaB ligand (RANKL). Anti-IL-1 or anti-TNFalpha therapies consistently reduce inflammation in these models, but systemic bone loss often persists. RANKL inhibition consistently prevents bone loss in both models without reducing joint inflammation. Effects of these therapies on systemic markers of bone turnover and inflammation have not been directly compared.

METHODS

Lewis rats with established AIA or CIA were treated for 10 days (from day 4 post onset) with either PBS (Veh), TNFalpha inhibitor (pegsunercept), IL-1 inhibitor (anakinra), or RANKL inhibitor (osteoprotegerin (OPG)-Fc). Local inflammation was evaluated by monitoring hind paw swelling. Bone mineral density (BMD) of paws and lumbar vertebrae was assessed by dual X-ray absorptiometry. Markers and mediators of bone resorption (RANKL, tartrate-resistant acid phosphatase 5b (TRACP 5B)) and inflammation (prostaglandin E2 (PGE2), acute-phase protein alpha-1-acid glycoprotein (alpha1AGP), multiple cytokines) were measured in serum (day 14 post onset).

RESULTS

Arthritis progression significantly increased paw swelling and ankle and vertebral BMD loss. Anti-TNFalpha reduced paw swelling in both models, and reduced ankle BMD loss in AIA rats. Anti-IL-1 decreased paw swelling in CIA rats, and reduced ankle BMD loss in both models. Anti-TNFalpha and anti-IL-1 failed to prevent vertebral BMD loss in either model. OPG-Fc reduced BMD loss in ankles and vertebrae in both models, but had no effect on paw swelling. Serum RANKL was elevated in AIA-Veh and CIA-Veh rats. While antiTNFalpha and anti-IL-1 partially normalized serum RANKL without any changes in serum TRACP 5B, OPG-Fc treatment reduced serum TRACP 5B by over 90% in both CIA and AIA rats. CIA-Veh and AIA-Veh rats had increased serum alpha1AGP, IL-1beta, IL-8 and chemokine (C-C motif) ligand 2 (CCL2), and AIA-Veh rats also had significantly greater serum PGE2, TNFalpha and IL-17. Anti-TNFalpha reduced systemic alpha1AGP, CCL2 and PGE2 in AIA rats, while anti-IL-1 decreased systemic alpha1AGP, IL-8 and PGE2. In contrast, RANKL inhibition by OPG-Fc did not lessen systemic cytokine levels in either model.

CONCLUSIONS

Anti-TNFalpha or anti-IL-1 therapy inhibited parameters of local and systemic inflammation, and partially reduced local but not systemic bone loss in AIA and CIA rats. RANKL inhibition prevented local and systemic bone loss without significantly inhibiting local or systemic inflammatory parameters.

ICOS promotes IL-17 synthesis in colonic intraepithelial lymphocytes in IL-10-/- mice

In the absence of IL-10, colonic inflammation ensues, which is characterized by high levels of IL-17. Here, we demonstrate a direct correlation between ICOS expression and IL-17 production in cIELs. IL-10(-/-) mice had increased numbers of cIELs and greater colon weight. Although the CD69 early activation antigen was expressed on cIELs from normal and IL-10(-/-) mice, ICOS was expressed only on cIELs from IL-10(-/-) mice. IL-17-producing cells in IL-10(-/-) mice consisted of CD4(+) and CD8(+) cIELs; however, CD4(+) cells were the predominant IL-17-producing cell population. Culture of cIELs from IL-10(-/-) mice with IL-23 resulted in an increase in ICOS and IL-17 expression, whereas IL-10 suppressed expression of ICOS and IL-17. This occurred in primary cultures and recall stimulation experiments. The ICOS ligand B7RP-1 was up-regulated on colonic epithelial cells and on a population of large granular leukocytes during inflammation. Culture of cIELs with B7RP-1(+) DCs enhanced IL-17A production from normal cIELs but failed to do so using cIELs from ICOS(-/-) mice. In vivo treatment of IL-10(-/-) mice with antibody to ICOS resulted in a significant reduction in colonic pathology. These findings implicate ICOS as an activational signal of Th17 cells during chronic intestinal inflammation, and they suggest that under some conditions, control of ICOS expression may help to suppress chronic intestinal inflammation.

Retinal Astrocytes respond to IL-17 differently than Retinal Pigment Epithelial cells

IL-17+ T cells make up the majority of the infiltrating cells in the inflamed eye during the development of EAU. However, the role of IL-17 in ocular inflammation is poorly defined. Given that the primary target cells for IL-17 are parenchymal cells of the tissue, we investigated the in vitro effect of IL-17 on mouse RACs and RPE cells. Our results showed that although RACs and RPE cells expressed the IL-17R, RACs responded to IL-17 by producing increased amounts of proinflammatory cytokines and chemokines, leading to increased migration of granulocytes, whereas RPE cells responded to the same concentration of IL-17 by expressing increased levels of SOCS proteins, resulting in only limited production of proinflammatory cytokines and chemokines and an increased amount of suppressive cytokines, such as LIF. The combination of IL-17 and IFN-gamma had a synergistic effect on cell migration with RACs but an antagonistic effect with RPE. In addition, specific inhibitors of the PI3K/Akt signaling pathway completely blocked inflammatory cell migration induced by chemokines released by IL-17-stimulated RACs. Our results demonstrate that IL-17 can induce a pro- or anti-inflammatory effect in the eye, depending on the parenchymal cells stimulated.

Cartilage homeostasis in health and rheumatic diseases

As the cellular component of articular cartilage, chondrocytes are responsible for maintaining in a low-turnover state the unique composition and organization of the matrix that was determined during embryonic and postnatal development. In joint diseases, cartilage homeostasis is disrupted by mechanisms that are driven by combinations of biological mediators that vary according to the disease process, including contributions from other joint tissues. In osteoarthritis (OA), biomechanical stimuli predominate with up-regulation of both catabolic and anabolic cytokines and recapitulation of developmental phenotypes, whereas in rheumatoid arthritis (RA), inflammation and catabolism drive cartilage loss. In vitro studies in chondrocytes have elucidated signaling pathways and transcription factors that orchestrate specific functions that promote cartilage damage in both OA and RA. Thus, understanding how the adult articular chondrocyte functions within its unique environment will aid in the development of rational strategies to protect cartilage from damage resulting from joint disease. This review will cover current knowledge about the specific cellular and biochemical mechanisms that regulate cartilage homeostasis and pathology.

IL-17 and Th17 cells in human inflammatory diseases

IL-17 was discovered in 1995/96 as a T cell derived cytokine with effects on inflammation and neutrophil activation. In 2006, the precise cell source of IL-17 was identified in the mouse, and these cells were named Th17 cells. They play a role in various human diseases associated with inflammation and destruction such as rheumatoid arthritis, psoriasis, Crohn's disease, multiple sclerosis, where IL-17 can be seen as a therapeutic target.

Changes in gene expression pattern of human primary macrophages induced by carbosilane dendrimer 2G-NN16

PURPOSE

The use of dendrimers for biomedical applications has emerged with promising results. 2G-NN16 is a carbosilane dendrimer with sixteen positive charges per molecule tested to be capable to bind and release antisense oligonucleotides (ODNs) and small interference RNA (siRNA) in vitro. In spite of low cytotoxicity observed for these dendrimers, little is known about cellular changes they produce in cells in general and in immune cells in particular.

MATERIALS AND METHODS

Genomic technologies allow us to identify global gene expression profile changes in macrophages exposed to a non-toxic concentration (5 microM) of 2G-NN16, alone or complexed with a random siRNA (dendriplex). Results were confirmed by quantitative real-time RT-PCR.

RESULTS

Exposing macrophages to this dendrimer or dendriplex causes multiple gene expression changes, but no specific action of random siRNA was detected. Pathway analysis of differentially expressed genes shows the altered functions to be immune response, proliferation and transcription regulation. Interleukin 17F (IL17F) was the most regulated gene.

CONCLUSIONS

Global gene expression profiles are a highly sensitive method to measure the toxicity degree of a gene delivery vehicle. The strong repression of IL17F, IL23R and IL23A, all of which are involved in autoimmune disease, by this particular dendrimer suggests a potential pharmacological application.

Synergism between tumor necrosis factor alpha and interleukin-17 to induce IL-23 p19 expression in fibroblast-like synoviocytes

In order to determine the mechanisms by which a chronic inflammatory network can be maintained in the arthritic joint, we examined whether fibroblast-like synoviocytes (FLS) could provide feedback signals after their stimulation by inflammatory cytokines. FLS and dermal fibroblasts (DF) were derived from rheumatoid arthritis (RA), osteoarthritis (OA) and post-trauma patients. These two cell types were then stimulated with 10 nanogram/ml of TNFalpha, IL-1beta and IL-17 alone or in combination treatments. Specific mRNA expression of IL-23 p19 was quantitated by real-time PCR and its protein by immunoprecipitation. A striking specific synergistic induction of IL-23 p19 versus IL-12 p35 mRNA expression was noted after stimulation with IL-17 and TNFalpha in FLS, and to a lesser degree in DF (p<0.043). This synergistic response was composed of an initial priming step by IL-17, thus making FLS hyperresponsive to TNFalpha-mediated stimulation. In contrast, IL-1beta mediated induction of IL-23 p19 expression was cell-specific. Induction of IL-23 p19 expression by IL-1beta was present in FLS but almost absent in the DF derived from the same patients. Furthermore, IL-1beta did not synergize with IL-17 to induce IL-23 p19 expression. Immunoprecipitation of FLS cellular lysates after stimulation with IL-17 and TNFalpha detected p19 protein and this was enhanced by the addition of IL-1beta. However, no co-immunoprecipitation of the p40 subunit of IL-23 was noted from the same cells. Thus, FLS are potently regulated by inflammatory cytokines to specifically express IL-23 p19. Additional byproducts of the inflammatory milieu may be required for the generation and secretion of bioactive IL-23.

Biological targets in the treatment of rheumatoid arthritis: a comprehensive review of current and in-development biological disease modifying anti-rheumatic drugs

Enhanced understanding of the rheumatoid arthritis (RA) pathophysiology and the role of cytokines has enabled the development of innovative biological agents in the last 10 years that target specific parts of the immune response. Failure to achieve adequate response with traditional disease modifying anti-rheumatic drugs (DMARDs) and increasing evidence of ongoing radiographic deterioration of the affected joints despite seemingly clinical response were essential stimuli for the development of biologics. The current and upcoming biological agents are primarily aimed at neutralizing circulating and cell-bound pro-inflammatory cytokines, interfering in the interaction of antigen-presenting and T-lymphocytes, eliminating circulating B-lymphocytes or by interfering with the intracellular signaling mechanisms of immuno-competent cells that lead to inflammation. These agents have improved the currently available treatments due to greater efficacy, fast action and greater tolerability. However, use of these agents has also been associated with significant, although rare, adverse events and considerable cost. Therefore, these agents should be used with caution by experienced clinicians. The present work aims to provide a global and updated review of the current and in-development biological DMARDs for the treatment of RA.

Altered kinetics of interleukin-6 and other inflammatory mediators during exercise in children with type 1 diabetes

BACKGROUND

Leukocyte mobilization and secretions of cytokines, chemokines, and growth factors in children during exercise are necessary biochemical signals for physiological growth and long-term cardiovascular protection. Because of glycemic instability, altered exercise responses, particularly the proinflammatory cytokine interleukin (IL)-6, may occur in type 1 diabetes mellitus (T1DM) that could influence the onset/progression of diabetic vascular complications. Relatively little is known, however, on most molecular aspects of immunomodulatory adaptation to exercise in diabetic children.

METHODS

We therefore studied 21 children (age, 13.4 +/- 0.3 years; 13 boys/8 girls) with T1DM and 21 age-matched healthy controls during 30 minutes of intense and intermittent cycling exercise. Euglycemia was maintained during and for greater than 90 minutes before exercise; blood samples for IL-6 and other cytokines/chemokines were drawn before, during (every 6 minutes), and after (every 15 minutes) exercise.

RESULTS

In T1DM, exercise-induced IL-6 peak occurred earlier and with greater magnitude than that in controls; an exploratory analysis of additional inflammatory mediators displayed a similarly accelerated/exaggerated pattern in T1DM, including the kinetic profiles of tumor necrosis factor alpha, IL-4, IL-12p70, IL-17, granulocyte-monocyte colony-stimulating factor, monocyte chemoattractant protein-1, macrophage inflammatory protein-1alpha, and eotaxin (interferon-inducible protein-10 was the only measured variable essentially indistinguishable between groups).

CONCLUSION

Therefore, during intense and intermittent exercise, significant alterations in the immunologic pattern of inflammatory regulation occurred in children with T1DM as compared with healthy controls. Our findings underscore how the understanding of all the underlying molecular mechanisms is a necessary prerequisite for achieving effective use of exercise and the full manifestation of its health benefits, particularly in understudied populations such as children with T1DM who are at increased risk for cardiovascular complications.

IRF-4-binding protein inhibits interleukin-17 and interleukin-21 production by controlling the activity of IRF-4 transcription factor

The T helper 17 (Th17) cell lineage is important in inflammatory and autoimmune responses, via its ability to produce interleukin-17 (IL-17) and IL-21. Given the potentially deleterious effects of Th17 cells, their generation needs to be strictly controlled. IRF-4 is a transcription factor that has recently emerged as a key regulator of Th17 cell differentiation. Here, we showed that mice deficient in a previously isolated protein, IBP (IRF-4-binding protein), rapidly developed rheumatoid arthritis-like joint disease and large-vessel vasculitis. The pathology was associated with an enhanced responsiveness of T cells to low levels of stimulation and with the inappropriate synthesis of IL-17 and IL-21. IBP sequestered IRF-4 and prevented it from targeting the transcriptional regulatory regions of the genes that encode IL-17 and IL-21. Thus, IBP appears to be important in preventing T cell-mediated autoimmunity by ensuring that the production of IL-17 and IL-21 does not occur in response to self-antigens.

Cells of the synovium in rheumatoid arthritis. Chondrocytes

Rheumatoid arthritis (RA) is one of the inflammatory joint diseases in a heterogeneous group of disorders that share features of destruction of the extracellular matrices of articular cartilage and bone. The underlying disturbance in immune regulation that is responsible for the localized joint pathology results in the release of inflammatory mediators in the synovial fluid and synovium that directly and indirectly influence cartilage homeostasis. Analysis of the breakdown products of the matrix components of joint cartilage in body fluids and quantitative imaging techniques have been used to assess the effects of the inflammatory joint disease on the local remodeling of joint structures. The role of the chondrocyte itself in cartilage destruction in the human rheumatoid joint has been difficult to address but has been inferred from studies in vitro and in animal models. This review covers current knowledge about the specific cellular and biochemical mechanisms that account for the disruption of the integrity of the cartilage matrix in RA.

Regulation of IL-17 production in human lymphocytes

The discovery of a new lineage of helper T cells that selectively produces interleukin (IL)-17 has provided exciting new insights into immunoregulation, host defense and the pathogenesis of autoimmune diseases. Although the factors that promote murine Th17 differentiation have been intensively examined, there has been much less information on the regulation of this cytokine in human T cells. IL-17 is readily produced by human memory T cells, which we now know exhibit distinct patterns of chemokine receptor expression and may differentiate in response to selective pathogens. Recently it has been shown that IL-1, IL-6 and IL-23 are important in driving human Th17 differentiation. However, TGFbeta-1 which is important for the differentiation of murine Th17 cells and inducible regulatory T cells (iTregs), is reportedly not required and even inhibits for human Th17 differentiation. In addition, human Th17 cells also produce other proinflammatory cytokines. Further characterization of the transcription regulation of human IL-17 expression, and the epigenetic regulation of human Il17 locus should improve our understanding the lineage commitment of human Th17 cells. Targeting the production and action of this cytokine is also likely to be beneficial therapeutically for autoinflammatory and autoimmune diseases.

Th17 cells: a new fate for differentiating helper T cells

Classically naïve CD4(+) have been thought to differentiate into two possible lineages, T helper 1 (Th1) or T helper 2 (Th2) cells. Within this paradigm the pathogenesis of autoimmunity was suggested to predominantly relate to Th1 cells and the production of IFN-gamma. However, there were many aspects of this model that did not seem to fit, not the least of which was that IFN-gamma was protective in some models of autoimmunity. During the past 2 years, remarkable progress has been made to characterize a new lineage of helper T cells. Designated Th17 cells, this lineage selectively produces proinflammatory cytokines including IL-17, IL-21, and IL-22. In the mouse, the differentiation of this new lineage is initiated by TGFbeta-1 and IL-6 and IL-21, which activate Stat3 and induce the expression of the transcription factor retinoic acid-related orphan receptor (RORgammat). IL-23, which also activates Stat3, apparently serves to maintain Th17 cells in vivo. In human cells, IL-1, IL-6, and IL-23 promote human Th17 differentiation, but TGFbeta-1 is reportedly not needed. Emerging data have suggested that Th17 plays an essential role in the host defense against extracellular bacteria and fungi and in pathogenesis of autoimmune diseases. Selectively targeting the Th17 lineage may be beneficial for the treatment of inflammatory and autoimmune diseases.

Interleukin-17 gene expression in patients with rheumatoid arthritis

Interleukin-17 is a proinflammatory cytokine. Recent animal studies have shown that IL-17 plays a role in the initiation and progression of arthritis. However, whether IL-17 has a prominent role in human rheumatoid arthritis (RA) or not remains unclear. Here we investigated the role of IL-17 in patients with RA. cDNA was prepared from knee joint synovial tissues of RA (n = 11) and osteoarthritic (OA, n = 10) patients and PBMC of RA (n = 52) and healthy subjects (n = 34). IL-17 gene expression level was measured by real-time PCR, and was compared with various clinical parameters. IL-17 gene expression in synovial tissues of RA was similar to that in OA. IL-17 gene expression level in PBMC of RA patients was significantly higher than in the control. The response (changes in DAS) to two-week treatment with anti-TNF-alpha blockers (infliximab or etanercept) did not correlate with changes in IL-17 gene expression levels. The IL-17/TNF-alpha gene expression ratio at baseline (before treatment) tended to be lower in responders to the treatment. Expression of IL-17 gene in PBMC may be associated with the inflammatory process of RA. IL-17/TNF-alpha expression ratio is a potentially suitable marker of response to anti-TNF-alpha therapy.

Tumor necrosis factor antagonist mechanisms of action: a comprehensive review

During the past 30 years, elucidation of the pathogenesis of rheumatoid arthritis, Crohn's disease, psoriasis, psoriatic arthritis and ankylosing spondylitis at the cellular and molecular levels has revealed that these diseases share common mechanisms and are more closely related than was previously recognized. Research on the complex biology of tumor necrosis factor (TNF) has uncovered many mechanisms and pathways by which TNF may be involved in the pathogenesis of these diseases. There are 3 TNF antagonists currently available: adalimumab, a fully human monoclonal antibody; etanercept, a soluble receptor construct; and infliximab, a chimeric monoclonal antibody. Two other TNF antagonists, certolizumab and golimumab, are in clinical development. The remarkable efficacy of TNF antagonists in these diseases places TNF in the center of our understanding of the pathogenesis of many immune-mediated inflammatory diseases. The purpose of this review is to discuss the biology of TNF and related family members in the context of the potential mechanisms of action of TNF antagonists in a variety of immune-mediated inflammatory diseases. Possible mechanistic differences between TNF antagonists are addressed with regard to their efficacy and safety profiles.

Distinct regulation of interleukin-17 in human T helper lymphocytes

OBJECTIVE

Interleukin-17 (IL-17)-producing T helper cells have been proposed to represent a separate lineage of CD4+ cells, designated Th17 cells, which are regulated by the transcription factor retinoic acid-related orphan receptor gammat (RORgammat). However, despite advances in understanding murine Th17 differentiation, a systematic assessment of factors that promote the differentiation of naive human T cells to Th17 cells has not been reported. The present study was undertaken to assess the effects on naive human CD4+ T cells of cytokines known to promote murine Th17 cells.

METHODS

Human naive and memory CD4+ T cells isolated from peripheral blood were activated and cultured with various cytokines. Cytokine production was measured by enzyme-linked immunosorbent assay and flow cytometry. Messenger RNA was measured by quantitative polymerase chain reaction.

RESULTS

In response to anti-CD3/anti-CD28 stimulation alone, human memory T cells rapidly produced IL-17, whereas naive T cells expressed low levels. Transforming growth factor beta1 and IL-6 up-regulated RORgammat expression but did not induce Th17 differentiation of naive CD4+ T cells. However, IL-23 up-regulated its own receptor and was an important inducer of IL-17 and IL-22.

CONCLUSION

The present data demonstrate the differential regulation of IL-17 and RORgammat expression in human CD4+ T cells compared with murine cells. Optimal conditions for the development of IL-17-producing T cells from murine naive precursors are ineffective in human T cells. Conversely, IL-23 promoted the generation of human Th17 cells but was also a very potent inducer of other proinflammatory cytokines. These findings may have important implications in the pathogenesis of human autoimmunity as compared with mouse models.